Manufacture of tetryl



Patented Aug. 6, 1946 MANUFACTURE OF TETRYL George WashingtonBatchelder, Mantua, N. J.,

assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., acorporation of Delaware No Drawing. Application September 25, 1943,Serial No. 503,839

12 Claims.

This invention relates to the manufacture of tetryl and particularly tothe production of tetryl by'the nitration of dimethylaniline solution insulfuric acid.

This application is a continuation-in-part of my co-pending applicationSerial No. 466,797 filed November 24, 1942.

Dimethylaniline solution as used herein designatesdimethylanilinedissolved in sulfuric acid. By acid ratio as usedhereinafter is meant the weight ratio of 100% nitric acid to 100%dimethylaniline.

In the manufacture of tetryl by the methods known to the art, ordinarilydimethylaniline solution is introduced into a nitrating agent, such asnitric acid alone or a mixture of nitric and sulfuric acids, wherebynitration of the aromatic ring takes place and one of the methyl groupsattached to the amino nitrogen atom is replaced by an N02 group, formingtetryl.

In the conventional method of manufacture,

this is usually accomplished by introducing the acid into a nitrationapparatus in such amount that the nitric acid-dimethylaniline ratio isrelatively low; adding dimethylam'line solution until the temperaturereaches a definite limit, generally 145 F.; and continuing the nitrationat this temperature until all the dimethylaniline'solution has beenadded. This requires about three hours and forty-five minutes whenstarting with approximately 1,500 pounds of said solution. During thisstage of the process, tetryl crystallizes in the nitrator. The nitratedcharge is held in the nitrator for some time after all thedimethylaniline solution has been introduced. The charge is then furtherprocessed by extracting the tetryl from the spent acid and purifying thecrude' product. This process and others heretofore employed have notbeen altogether satisfactory because of the dangers and low productivecapacity attending the same.

While most accidents have occurred after a large amount of the tetrylcrystallized, said crystallization being promoted by the use ofinsufficient acid ratios, there is no evidence in the prior art thatthis fact even has been appreciated.

An object of this invention is a new and im proved process for theproduction of tetryl. Another object is a process of enhanced safety forthe manufacture of tetryl. A further object-is a method for theproduction of tetryl characterized by a remarkable increase inproductive capacity. These and additional objects of my invention willbecome apparent on reading this specification.

- of dimethylaniline used; that'is, increasing the 2 I have found thatthese objects are accomplished and the foregoing drawbacks overcome byincreasing the parts of mixed acid per part nitric acid ratio; heatingthe mixed acid before introduction into the nitrator; and increasingthe.

temperature of nitration. These objects may be.

obtained according to the present invention by operating under theforegoing conditions and (1) maintaining the nitration temperaturebetween and 180 F., for instance F., throughout the nitration andfeeding the dimethylaniline.

solution into the nitrator until a substantial portion of the nitricacid has been consumed; (2) or maintaining the nitration temperaturebetween 150 and F. and terminating the reaction by discontinuing theaddition of dimethylaniline solution at such time as to leave a largerexcess of nitric acid in the nitrator; (3) or keep-- ing the nitrationtemperature between 150 and 180 F. preferably between 165 and 180 F.,until about two-thirds of the dimethylaniline solutionhas beenintroduced, and keeping said temperature between 140 and 160 F. duringthe latter part of the reaction. In the first and third cases, the rateof feed of dimethylaniline solution may be somewhat greater before someof the tetryl crystallizes than thereafter. By operating under theseconditions, I am able to hold in solution a substantial amount of thetetryl as it is produced and throughout the remainder of the nitration.

While the acid ratio employed in either of the three cases specified mayrange preferably from '7 to 12, in any event it will be at least 7.

I have found that the point at which the tetryl begins to crystallizedepends primarily upon the temperature and acid ratio employed. Further,I have found that temperatures and rates of dimethylaniline solutionfeed, which are unsafe subsequent to the time when a portion of thetetryl begins to crystallize, can be employed safely prior to said time.However, the higher of two moderately high temperatures may be thesafer, because the time during which solid tetryl is present in thenitrator is diminished.

The following is set forth as an example of the process of my inventionhereinabove outlined, which, of course, is not intended to limit theinvention, but rather is cited as a specific embodiment thereof. tailssufficient to enable anyone skilled in the art to practice saidinvention.

One thousand, five hundred and eighty-eight pounds of mixed acidpreheated to 155 F. in-- This example gives de-- the cooking period.

eluding 1,247 pounds nitric acid, 167 pounds sulfuric acid, and 174pounds water, is introduced into the nitrator. After the mixed acid hasbeen introduced, the temperature is 135 F., and the agitator is startedat 140 R. P. M. A substantially constant and rapid flow of approximatela dimethylaniline solution is begun, and the temperature is brought toand maintained at 160 F. 7

tem, comprising a water jacket surroundingthe' nitrator and coils withinsaid nitrator, is used to maintain a constant temperature. When theaddition of dimethylaniline solution is complete, nitration is continuedfor minutes under substantially the same conditions of temperature andagitation, the latter period being referred to as At this stage of theprocess, agitation is reduced to 60 R; P. and the charge is eitherdrowned in water in the drowning tub, if the spent acid is to bediscarded, or cooled and filtered, if said acid is to be recovered. Ifsaid charge is drowned, this is done gradually so as to prevent anexcessive temperature in the drowning tub. Next, the drowned acid orspent acid is removed from the tetryl and some of the impurities arehydrolyzed by a thorough washing treatment with water. In continuing theprocess, the Washed tetryl is filtered, acetone refined, dried,screened, and packed.

As will be noticed by simple calculation, the acid ratio of the aboveexample is approximately 10. With this ratio, and a temperature of 160F. substantially all of the tetryl is held in solution throughout thenitration. I find it advantageous to use a nitrating acid, preheated tobetween 140" and 160 F. containing between 5% and 15% H2504 and between75% and 82% HNOa.

The dimethylaniline solution in sulfuric acid desirably will containbetween 8% and 12% of the former. The rate of addition of said solutionmay be such that between about 1,000 and 2,000 pounds are addedper hour.The nitration mixture may be maintained between 140 and 180 F. forbetween approximately 10 and 30 minutes after the nitration reaction issubstantially complete.

The advantages of my invention are very considerable. By (1) using anacid ratio of at least *7, preferably between 7 and 12, and maintainingthe nitration temperature between150 and 180 F., for instance 170 F.,throughout the nitration and feeding the dimethylaniline solution intothe nitrator until a substantial portion of the nitric acid has beenconsumed; (2) or by using an acid ratio between '7 and 12, preferablyabout 10, and maintaining the nitration temperature between 150" and 180F., for instance 170 F., and terminating the reaction by discontinuingthe addition of dimethylaniline solution whil a larger excess of nitricacid remains in the nitrator; (3) or by using an acid ratio of at least7, preferably between 7 and 12, and maintaining the nitrationtemperature between 150 and 180 F., desirably between 165 and 180 duringa substantial portion of the process, for example, until abouttwo-thirds of the dimethylanilinesolution has been introduced, andthereafter keeping said temperature between 140 and 160 F. durin thelatter part of the reaction; I am able to complete the reaction whileholding from at least two-thirds to all of the tetryl in solution and tolessen the time of nitration materially, thereby greatly increasing theamount of tetryl per manhour per nitrator, and simultaneously minimizingthe difiiculties of the nitration process, particularly the latter partthereof.

The fact that I am able to keep substantially more of the tetryl insolution throughout the nitration than is possible according to theprior art methods even at high temperatures is due to a great. extent tomy use of high acid ratios and high temperatures. The amount of tetrylwhich can be maintained dissolved in a given nitrator charge, otherconditions being equal, depends upon th acid ratio and temperatureemployed. Said amount of dissolved tetryl varies directly, up to a givenpoint, with the acid ratio. If practically allof the tetryl is notmaintained in solution during the nitration, gases collect in the chargeand their escape therefrom is seriously impeded by the layer ofcrystallized tetryl floating on the charge. This causes difficultieseven with temperatures just suificiently high to render the processcommercially feasible, said difficulties occurring particularly duringthe latter part of the nitration. Obviously the shorter the periodduring which solid tetryl is present, the safer the operation, in viewof the foregoing statements.

According to the present invention, said difficulties are obviated byemploying a high acid ratio. As a result of using high acid ratios, thenitration is carried out at higher temperatures without a sacrifice ofthe improved safety features according to my invention, therebyincreasing the output of a given nitrator.

Since it is a known fact that practically all abnormal frothing andfoaming, resulting in overflowing the nitrator and quite often producingfires, have occurred toward th end of the nitration, after a substantialpart of the tetryl crystallized, the improvements according to myinvention will be appreciated.

Although I have described my invention in detail and have thereforeutilized certain specific terms and language therein, it is tobeunderstood that the present disclosur is illustrative, rather thanrestrictive, and that many variations may be made therein which willstill be comprised within its scope. For instance, although in theexample given the heat of reaction is removed from the nitrator by meansof a Water jacket and water cooling coils, said heat may be removed bycold air or other cooling means. Also, it is feasible to employ aheating system other than steam. Thus, the speed of the agitator, degreeof temperature, and quantity and concentrations of materials used may bevaried to a certain extent. Nor is it essential that the mixed acid beheated before introduction into the nitrator, since this may be heatedafter it has passed to the nitrator. It is to be understood, therefore,that the invention is not limited to any specific form, composition,procedure, or embodiment except as indicated by the appended claims.

I claim:

1. A process of producing tetryl which comprises passing a mixed acid,including sulfuric and nitric acids, into a nitration apparatus;introducing a solution of dimethylaniline in sulfuric acid into saidnitrator, the ratio of nitric acid to dimethylaniline being at least 7to 1; agitating the charge throughout the nitration process; maintainingthe nitration temperature between and F, during said process until atleast two-thirds of said dimethylaniline solution has been added; andthereafter recovering the tetryl.

2. The process according to claim 1, in; which the tetry1 is recoveredby sufficiently cooling said charge at the end of the nitration to bringabout crystallization of the tetryl, and filterin the crystallizedtetryl from the spent acid.

3. The process according to claim 1, in which the tetry1 is drowned inwater before recovery.

4. The process according to claim 1, in which said nitration mixture ismaintained between 140 and 180 F. for between and 30 minutes after thenitration reaction is substantially complete.

5. A process of producing tetryl which comprises passing a mixed acid,including sulfuric and nitric acids, into a nitration apparatus;introducing a solution of dimethylaniline in sulfuric acid graduallyinto said nitrator, the ratio of nitric acid to dimethylaniline being atleast '7 to 1; agitating the charge throughout the nitration process;maintaining the temperature of nitration between 150 and 180 F. duringsaid process until at least two-thirds of said dimethylaniline solutionhas been introduced; reducing the temperature to between 140 and 160 F.and continuing the nitration; and thereafter recovering the tetryl.

6. A process of producing tetryl which comprises passing a mixed acid,including sulfuric and nitric acids, into a nitration apparatus;introducing a solution of dimethylaniline in sulfuric acid into saidnitrator at a sufiiciently constant rate of flow, the ratio of nitricacid to dimethylaniline being between '7 to 1 and 12 to 1; agitating thecharge throughout the nitration process; maintaining the temperature ofnitration between 165 and 180 F. until about two-thirds of saiddimethylaniline solution has been added; reducing the temperature tobetween 140 and 160 F. and continuing the nitration; and thereafterrecovering said tetryl.

7. A process of producing tetryl which comprises passing a mixed acid,including sulfuric and nitric acids, into a nitration apparatus;introducing a solution of dimethylaniline in sulfuric acid into saidnitrator until a substantial portion of the nitric acid has beenconsumed, the ratio of nitric acid to dimethylaniline being at least 7to 1; agitating the charge throughout the nitration process; maintainingthe temperature of said nitration between 150 and 180 F. throughout thenitration; and thereafter recoverin the tetry1.

8. A process of producing tetryl which comprises passing a mixed acid,including sulfuric and nitric acids, into a nitration apparatus;introducing a solution of dimethylaniline in sulfuric acid into saidnitrator until a substantial part of the nitric acid has been consumed,the ratio of nitric acid to dimethylaniline being at least 7 to 1;agitating the charge throughout the nitration process; maintaining thetemperature of said nitration at 170 F. throughout the nitration; andthereafter recovering the tetryl.

9. A process of producing tetry1 which comprises passing a mixed acid,including sulfuric and nitric acides, into a nitration apparatus;introducing a solution of dimethylaniline in sulfuric acid into saidnitrator, the ratio of nitric acid to dimethylaniline being between 7 to1 and 12 to 1; agitating the charge throughout the nitration process;maintaining the temperature of said nitration between and 180 F.throughout the nitration; discontinuing the addition of saiddimethylaniline solution while an excess of nitric acid remains in thenitrator; and thereafter recovering the tetryl.

10. A process of producing tetryl which comrises passing a mixed acid,including sulfuric and nitric acids, into a nitration apparatus;introducing a solution of dimethylaniline in sulfuric acid into saidnitrator, the ratio of nitric acid to dimethylaniline being about 10 to1; discontinuing the addition of said dimethylaniline solution while anexcess of nitric acid remains in the nitrator; agitating the chargethroughout the nitration process; maintaining the temperature of saidnitration at 170 F. throughout the nitration reaction, thereby holdingsubstantially all of the tetry1 in solution; and thereafter recoveringthe tetryl.

1 1.' A process of producing tetryl which comprises introducing apreheated mixed acid, including sulfuric and nitric acids, into anitration apparatus; introducing a solution comprising between 8% and12% of dimethylaniline in sulfuric acid into said nitrator at apractically constant rate of flow in order to introduc between 1,000 and2,000 pounds of said solution per hour, the ratio of nitric acid todimethylaniline being between 7 to 1 and 12 to 1; agitating thenitration mixture throughout the nitration process; maintaining thetemperature of said nitration between 150 and 180 F. until at leasttwo-thirds of said dimethylaniline solution has been introduced,reducing the temperature to between 140 and F. and continuing thenitration; drowning said charge in water; and thereafter recovering thetetryl.

12. A process of producing tetryl which comprises introducingapproximately 1,600 pounds of a mixed acid preheated to between 140 and160 F., including between approximately 5% and 15% H2504 and betweenabout 75% and 82% HNOs into a nitration apparatus; introducing asolution comprising between 8% and 12% of dimethylaniline in sulfuricacid into said nitrator at a sufficiently constant rate of flow so as tointroduce between 1,000 and 2,000 pounds of said solution per hour, theratio of nitric acid to dimethylaniline being at least 7 to 1; agitatingthe nitration mixture throughout the nitration process; maintaining thenitration temperature between and F. until at least two-thirds of saiddimethylaniline solution has been introduced; maintaining saidtemperature between 140 and 160 F. during the latter part of thenitration; cooling said charge sufiiciently to bring aboutcrystallization of the tetryl; and filtering said crystallized tetrylfrom the waste acid.

GEORGE WASHINGTON BATCHELDER.

